Енергија јонизације — разлика између измена
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{{short description|Minimum amount of energy required to remove an electron from an atom or molecule in the gaseous state}}
[[File:First Ionization Energy.svg|thumb|350x350px|Ionization energy trends plotted against the [[atomic number]]. The ionization energy gradually increases from the [[alkali metals]] to the [[noble gas]]es. The maximum ionization energy also decreases from the first to the last row in a given column, due to the increasing distance of the valence electron shell from the nucleus.]]
'''Енергија јонизације''' (''-{Ei}-'') је најмања количина [[Енергија|енергије]] коју је потребно довести једном [[атом]]у неког елемента да би он отпустио свој последњи, најслабије везани [[електрон]] са последњег [[Енергетски нивои|електронског нивоа]].<ref>Brady, J.E., Holum, J.R.,Chemistry. {{page1|location=|publisher=John Wiley & Sons|year=1993|isbn=978-0-471-59979-1|pages=}}</ref><ref name="Atkins7th">{{Atkins7th}}</ref><ref>{{Cite web|date=2013-10-02|title=Periodic Trends|url=https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Modules_and_Websites_(Inorganic_Chemistry)/Descriptive_Chemistry/Periodic_Trends_of_Elemental_Properties/Periodic_Trends|access-date=2020-09-13|website=Chemistry LibreTexts|language=en}}</ref> It is quantitatively expressed as
:X(g) + energy ⟶ X<sup>+</sup>(g) + e<sup>−</sup>
where X is any atom or molecule, X<sup>+</sup> is the ion with one electron removed, and e<sup>−</sup> is the removed electron.<ref name=Miessler>{{cite book |last1=Miessler |first1=Gary L. |last2=Tarr |first2=Donald A. |title=Inorganic Chemistry |date=1999 |publisher=Prentice Hall |isbn=0-13-841891-8 |page=41 |edition=2nd}}</ref> This is generally an [[endothermic process]]. As a rule, the closer the outermost electrons to the [[atomic nucleus|nucleus of the atom]], the higher the atom's ionization energy.
The sciences of physics and chemistry use different units for ionization energy.<ref>{{cite web|url=https://www.britannica.com/science/ionization-energy|title=Ionization energy|others= The Editors of Encyclopædia Britannica |date=May 29, 2020|website=britannica.com|publisher=Encyclopædia Britannica|access-date=November 3, 2020}}</ref> In physics, the unit is the amount of energy required to remove a single electron from a single atom or molecule, expressed as [[electronvolt]]s. In chemistry, the unit is the amount of energy required for all of the atoms in a [[Mole (unit)|mole]] of substance to lose one electron each: molar ionization energy or approximately [[enthalpy]], expressed as [[Joule#Multiples|kilojoule]]s per mole (kJ/mol) or [[Calorie|kilocalories]] per mole (kcal/mol).<ref>{{cite web|url=http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/Periodic_Table_of_the_Elements/Ionization_Energy|title=Ionization Energy|work = ChemWiki | publisher=University of California, Davis|date=2013-10-02}}</ref>
Енергија јонизације је веома важна мера реактивности одређеног [[Хемијски елемент|елемента]]. Вредност енергије јонизације дуж групе опада, што се објашњава порастом пречника атома и последичним падом јачине привлачних електростатичких сила између валентног електрона и језгра.<ref>{{cite web| date=January 15, 2018 | title=Chapter 9: Quantum Mechanics | url=http://faculty.chem.queensu.ca/people/faculty/mombourquette/FirstYrChem/Theory/ | access-date= October 31, 2020 | website= faculty.chem.queesu.ca | language=en}}</ref> Како су ове силе слабије, електрон се лакше отпушта, а побуђивање атома захтева мању количину енергије. Притом, прва енергија јонизације је најмања док је свака следећа значајно већа. У екстремним случајевима, друга енергија јонизације је и 1.000 пута већа од прве, као што је то случај код [[Алкални метали|алкалних метала]] где се након прве јонизације постиже стабилна [[електронска конфигурација]], са попуњеним октетом и јачим интраатомским силама између језгра и валентних електрона. Насупрот томе, енергија јонизације дуж периоде расте јер све већи број електрона у истом енергетском нивоу више интереагује са језгорм и отежава отпуштање валентних електрона, тј потребно је довести све већу количину енергије да би се валентни електрон(и) отпусито и на тај начин постигао стабилну електронску конфигурацију.
The ''n''th ionization energy refers to the amount of energy required to remove an electron from the species having a charge of (''n''-1). For example, the first three ionization energies are defined as follows:
:1st ionization energy is the energy that enables the reaction X ⟶ X<sup>+</sup> + e<sup>−</sup>
:2nd ionization energy is the energy that enables the reaction X<sup>+</sup> ⟶ X<sup>2+</sup> + e<sup>−</sup>
:3rd ionization energy is the energy that enables the reaction X<sup>2+</sup> ⟶ X<sup>3+</sup> + e<sup>−</sup>
The term ''ionization potential'' is an older and obsolete term<ref>{{Cite web|title=IUPAC - ionization potential (I03208)|url=http://goldbook.iupac.org/terms/view/I03208|access-date=2020-09-13|website=goldbook.iupac.org}}</ref> for ionization energy,<ref>{{cite book |first1=F. Albert |last1=Cotton |author1-link=F. Albert Cotton |first2=Geoffrey |last2=Wilkinson |author2-link=Geoffrey Wilkinson |title=Advanced Inorganic Chemistry |edition=5th |publisher=John Wiley |date=1988 |page=1381 |isbn=0-471-84997-9}}</ref> because the oldest method of measuring ionization energy was based on ionizing a sample and accelerating the electron removed using an [[Particle accelerator#Electrostatic particle accelerators|electrostatic potential]].
The most notable factors affecting the ionization energy include:
* Electron configuration: this accounts for most element's IE, as all of their chemical and physical characteristics can be ascertained just by determining their respective electron configuration.
* Nuclear charge: if the nuclear charge ([[atomic number]]) is greater, the electrons are held more tightly by the nucleus and hence the ionization energy will be greater.
* Number of [[electron shell]]s: if the size of the atom is greater due to the presence of more shells, the electrons are held less tightly by the nucleus and the ionization energy will be lesser.
*[[Effective nuclear charge]] (''Z''<sub>eff</sub>): if the magnitude of electron [[Shielding effect|shielding]] and penetration are greater, the electrons are held less tightly by the nucleus, the ''Z''<sub>eff</sub> of the electron and the ionization energy is lesser.<ref>{{Cite journal|last1=Lang|first1=Peter F.|last2=Smith|first2=Barry C.|title=Ionization Energies of Atoms and Atomic Ions|journal=Journal of Chemical Education|language=en|volume=80|issue=8|pages=938|doi=10.1021/ed080p938|bibcode=2003JChEd..80..938L|year=2003}}</ref>
* Type of [[Atomic orbital|orbital]] ionized: an atom having a more stable [[Electron configuration|electronic configuration]] has less tendency to lose electrons and consequently has higher ionization energy.
* Electron occupancy: if the highest occupied [[Atomic orbital|orbital]] is doubly occupied, then it is easier to remove an electron.
Other minor factors include:
* Relativistic effects: heavier elements (especially those whose [[atomic number]] is greater than 70) are affected by these as their electrons are approaching the speed of light, and hence have a smaller atomic radius/higher IE.
* Lanthanide and actinide contraction (and scandide contraction): the unprecedented shrinking of the elements affect the ionization energy, as the net charge of the nucleus is more strongly felt.
*[https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Electronic_Structure_of_Atoms_and_Molecules/Electronic_Configurations/Spin_Pairing_Energy Electron pair energies] and [[exchange energy]]: these would only account for fully filled and half-filled orbitals. A common misconception is that "symmetry" plays a part; albeit, none so far has concluded its evidence.
== Одређивање енергија јонизације ==
[[File:Measurement of ionization energy of atoms - schematic.svg|thumb|304x304px|Ionization energy measurement apparatus. |alt=]]
Ionization energy of atoms, denoted ''E''<sub>i</sub>, is measured<ref>{{Cite web|last=Mahan|first=Bruce H.|date=1962|title=Ionization Energy|url=https://archive.org/details/ionization_energy|access-date=2020-09-13|publisher=College of Chemistry, University of California Berkeley}}</ref> by finding the minimal energy of light quanta ([[photon]]s) or electrons accelerated to a known energy that will kick out the least bound atomic electrons. The measurement is performed in the gas phase on single atoms. While only noble gases occur as monoatomic gases, other gases can be split into single atoms. Also, many solid elements can be heated and vaporized into single atoms. Monoatomic vapor is contained in a previously evacuated tube that has two parallel electrodes connected to a voltage source. The ionizing excitation is introduced through the walls of the tube or produced within.
When ultraviolet light is used, the wavelength is swept down the ultraviolet range. At a certain wavelength (λ) and frequency of light (ν=c/λ, where c is the speed of light), the light quanta, whose energy is proportional to the frequency, will have energy high enough to dislodge the least bound electrons. These electrons will be attracted to the positive electrode, and the positive ions remaining after the [[photoionization]] will get attracted to the negatively charged electrode. These electrons and ions will establish a current through the tube. The ionization energy will be the energy of photons ''hν''<sub>i</sub> (''h'' is the [[Planck constant]]) that caused a steep rise in the current: ''E''<sub>i</sub>=''hν''<sub>i</sub>.
When high-velocity electrons are used to ionize the atoms, they are produced by an [[electron gun]] inside a similar evacuated tube. The energy of the electron beam can be controlled by the acceleration voltages. The energy of these electrons that gives rise to a sharp onset of the current of ions and freed electrons through the tube will match the ionization energy of the atoms.
== Вредности и трендови ==
Generally, the (''n''+1)th ionization energy of a particular element is larger than the ''n''th ionization energy. When the next ionization energy involves removing an electron from the same electron shell, the increase in ionization energy is primarily due to the increased net charge of the ion from which the electron is being removed. Electrons removed from more highly charged ions experience greater forces of electrostatic attraction; thus, their removal requires more energy. In addition, when the next ionization energy involves removing an electron from a lower electron shell, the greatly decreased distance between the nucleus and the electron also increases both the electrostatic force and the distance over which that force must be overcome to remove the electron. Both of these factors further increase the ionization energy.
[[File:Ionization energies of atoms - labeled - atomic orbital filling indicated.svg|thumb|350x350px|Ionization energies peak in noble gases at the end of each period in the periodic table of elements and, as a rule, dip when a new orbital is starting to be filled.]]
Some values for elements of the third period are given in the following table:
{| class="sortable"
|+''Successive ionization energy values /'' [[joule|kJ]]/[[mole (unit)|mol]]<sup>−1</sup> <br> (96.485 kJ/mol ≡ 1 [[electron volt|eV]])
|-
! Element
! First
! Second
! Third
! Fourth
! Fifth
! Sixth
! Seventh
|- align="right"
! align="center" | [[Sodium|Na]]
| 496
| 4,560 || || || || ||
|- align="right"
! align="center" | [[Magnesium|Mg]]
| 738
| 1,450
| 7,730 || || || ||
|- align="right"
! align="center" | [[Aluminium|Al]]
| 577
| 1,816
| 2,881
| 11,600 || || ||
|- align="right"
! align="center" | [[Silicon|Si]]
| 786
| 1,577
| 3,228
| 4,354
| 16,100 || ||
|- align="right"
! align="center" | [[Phosphorus|P]]
| 1,060
| 1,890
| 2,905
| 4,950
| 6,270
| 21,200 ||
|- align="right"
! align="center" | [[Sulfur|S]]
| 1,000
| 2,295
| 3,375
| 4,565
| 6,950
| 8,490
| 27,107
|- align="right"
! align="center" | [[Chlorine|Cl]]
| 1,256
| 2,260
| 3,850
| 5,160
| 6,560
| 9,360
| 11,000
|- align="right"
! align="center" | [[Argon|Ar]]
| 1,520
| 2,665
| 3,945
| 5,770
| 7,230
| 8,780
| 12,000
|}
Large jumps in the successive molar ionization energies occur when passing [[noble gas]] configurations. For example, as can be seen in the table above, the first two molar ionization energies of magnesium (stripping the two 3s electrons from a magnesium atom) are much smaller than the third, which requires stripping off a 2p electron from the [[neon]] configuration of Mg<sup>2+</sup>. That electron is much closer to the nucleus than the 3s electron removed previously.
Ionization energy is also a [[periodic trends|periodic trend]] within the periodic table. Moving left to right within a [[Period (periodic table)|period]], or upward within a [[Group (periodic table)|group]], the first ionization energy generally increases,<ref name=":1">{{cite web |url=https://www.chem.tamu.edu/class/fyp/stone/tutorialnotefiles/fundamentals/trends.htm |title=Atomic Structure : Periodic Trends |last=Stone |first=E.G. |date=December 19, 2020 |department=Department of Chemistry |website=chem.tamu.edu |publisher=Texas A&M University |location=400 Bizzell St, College Station, TX 77843, Texas, United States |language=en |access-date=December 19, 2020}}</ref> with exceptions such as aluminium and sulfur in the table above. As the nuclear charge of the nucleus increases across the period, the [[Shielding effect|electron shielding]] remains constant, hence the [[atomic radius]] decreases, and the electron cloud becomes closer towards the nucleus<ref>{{Cite web|title=Anomalous trends in ionization energy|url=https://chemistry.stackexchange.com/questions/32363/anomalous-trends-in-ionization-energy|access-date=2020-09-20|website=Chemistry Stack Exchange}}</ref> because the electrons, especially the outermost one, are held tighter by the higher effective nuclear charge. Similarly on moving upward within a given group, the electrons are held in lower-energy orbitals, closer to the nucleus and therefore are more tightly bound.<ref name=":2">{{Cite web|title=Ionization Energy {{!}} Introduction to Chemistry|url=https://courses.lumenlearning.com/introchem/chapter/ionization-energy/|access-date=2020-09-13|website=courses.lumenlearning.com}}</ref>
== Референце ==
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== Литература ==
{{refbegin}}
* Tro, Nivaldo J. (2008). ''Chemistry: A Molecular Approach'' (2nd Edn.). New Jersey: [[Pearson Prentice Hall]]. {{ISBN|0-13-100065-9}}. pp. 348–349.
* {{cite book|last=Jolly|first= William L. |year=1991|title=Modern Inorganic Chemistry|edition=2nd| location=New York|publisher=[[McGraw-Hill]]|isbn= 978-0-07-112651-9|pages=71–76}}
* {{Cite book| last=Mullay|first=J. |title=Electronegativity |year=1987|chapter=Estimation of atomic and group electronegativities|volume=66|pages=1–25| doi=10.1007/BFb0029834| series=Structure and Bonding| isbn=978-3-540-17740-1}}
{{refend}}
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